Synthesis of diketopyrrolopyrrole-derived maleimides — new turn-on fluorescent probes for detecting biothiols

A convenient synthesis of mono- and bis(aminophenyl)diketopyrrolopyrrole derivatives, and their conversion to diketopyrrolopyrrole-derived maleimides is reported. The ability of the new maleimides to act as turn-on fluorescent probes for the detection of cysteine, homocysteine or glutathione was evaluated and, remarkably, the limits of detection (LOD) were excellent, with one probe achieving 18 nM for cysteine within just 5 minutes. The new compounds exhibited Stokes shifts ranging from 66 and 73 nm. A convenient synthesis of DPP-derived maleimides that function as effective turn-on fluorescent probes for biothiol detection. • Convenient synthesis of mono- and bis(aminophenyl)diketopyrrolopyrroles from Pigment Red 254. • Simple access to non-fluorescent diketopyrrolopyrrole-derived maleimides. • Diketopyrrolopyrrole-derived maleimides serve as efficient turn-on fluorescent probes for biothiol detection.